understanding of the prospects for IFE. Over the next several years, experiments will be ongoing at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) that are aimed at achieving ICF ignition. At the same time, experiments such as those at the University of Rochester’s Laboratory for Laser Energetics, the Naval Research Laboratory, Lawrence Berkeley Laboratory, and Sandia National Laboratories continue to advance our understanding and control of ICF using different technology and physics approaches. However, it should be recognized that up to this point, the majority of the funding and efforts related to ICF target physics are provided by—and related to—the U.S. nuclear weapons program and its stockpile stewardship efforts and are not directly aimed at energy applications.
DOE’s Centurion-Halite program revolved around a series of underground experiments conducted in the 1980s in which target capsules were driven by the energy from nuclear explosions. Additional discussion of the program is provided in classified Appendix D.
Target Design: Direct and Indirect Drive, Z-Pinch
There are two major concepts for ICF target design: direct-drive targets, in which the driver energy (e.g., in the form of laser beams, particle beams, or magnetic field pressure) directly strikes the fuel capsule (see Figure 2-1); and indirect-drive targets, in which the driver energy first strikes a hollow chamber (a “hohlraum”) surrounding the fuel capsule, producing energetic X-rays that compress the fuel capsule (see Figure 2-2). Conventional direct and indirect drive share many key physics issues, such as energy coupling, the need for driver uniformity, and hydrodynamic instabilities; however, there are issues that are unique to each concept.
Generally, the elements of the fuel capsule are similar for direct drive and indirect drive, at least with respect to laser drivers. Fuel capsules are typically spherical, with several layers: an outer ablator layer; a layer of cryogenic frozen fuel; and a center of gaseous fuel, typically deuterium-tritium (DT). A sample fuel capsule is shown in Figure 2-3.
Several of the key differences between direct drive and indirect drive for ICF are discussed briefly in the sections that follow.
Direct-drive concepts for ICF using laser drivers are currently being researched at the University of Rochester’s Laboratory for Laser Energetics (LLE) and the Naval Research Laboratory (NRL). Concepts using heavy-ion beam drivers are being